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I have a fascination with older calculating devices, especially HP calculators and slide rules from various makers. And, so, I spend my book and article earnings on buying them.
Back when I were a lad taking O-levels in England at the tender age of 16, you were allowed to take in slide rules into the exams. In fact, if I recall correctly, you had to have one for the Maths O-level since there were some questions that needed you to use it to get the answer. I had a fairly cheap Blundell-Harling for my exams, but it was a duplex — that is, it had scales on both sides — so I felt like I was the man. In reality I wasn't, since the only operations you had to do were multiplication and division, but the 'tude is everything.
This was in 1973, which is the interesting tipping point for portable calculating devices. That year, Hewlett-Packard released their HP 35 calculator, the first really portable scientific electronic calculator. At a stroke, slide rules were doomed. Nevertheless, after well over 300 years of development, the final slide rules were beautiful well-machined works of art, let alone reasonably accurate calculating devices.
Keuffel and Esser (K&E) were a US manufacturer of slide rules. and the Deci-Lon (model number 68-1100) was its crème de la crème: a wide duplex slide rule with 26 scales. Two color, plastic, a racy forward-looking logo, and with the end pieces of the slide roughened so your fingers didn't slip in the heat of a calculation.
On Monday, the mailman brought the one I'd bought to add to my small collection. It was in a very nice condition indeed.
Front side:
Back side:
(Click on each image for a giant-sized view.)
With it was a leather case, the usual K&E orange-brown. The belt loop was missing (yes, you could clip your slide rule to your belt so it was on hand at every moment.) No manual, however I've just scored one from a specialist.
Using the rather arcane dating algorithms for K&E slide rules, this one seems to be dated around 1962, the year of its introduction.
Now playing:
Boo, Betty - Wish you were here
(from Grrr! It's Betty Boo)
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11 Responses
#1 schalk versteeg said...
03-Dec-08 11:26 PMHi Julian,
Although I had one in school and was fascinated by it, I never learned how they work (I am a bit young).
With you bringing them up I thought it might be interesting to also add how they work (http://www.sphere.bc.ca/test/howto.html) and wikipedia (http://en.wikipedia.org/wiki/Slide_rule).
If you can add anything more please do.
#2 julian m bucknall said...
07-Dec-08 8:08 PMI'll be glad to write a little intro to using a slide rule. It's a fascinating subject to be sure, and I've just received the manual for the Deci-Lon (it's great: each section has a set of exercises -- just like an old Mathematics book).
Cheers, Julian
#3 Van Swofford said...
08-Dec-08 10:16 AMHi Julian,
Neat! I was the slide rule geek in high school, then spent my life savings of $400 for an HP-45 when I started college in '73.
As a pilot on our flying team, I became the guru on the E-6B flight computer, which is just a circular slide rule with some specialized aviation functions added.
Fun stuff!
Cheers,
Van
#4 Don Clarke said...
14-Jan-09 9:19 AMI have a few Sliders myself as well as a few circulars rules. Engineer by trade these got me through my degree, as I was so broke I couldn't afford a calculator. But now I use them to design my r/c airplanes.
Now my kids want to learn to use them for their calc classes. As the prof doesn't concider them to be real calculators. Young whip should figure out what sent us into space and probably designed the car that he was conceived in.
I even have a 8 1/2 inch circular that was owned by R.P. Eccles. He was one of the lead engineers on the "Manhattan Project". heck of a history. Don't ya think?
hava a good one,
Don
#5 David Pallo said...
02-Sep-11 9:32 AMI have a Deci-lon slide rule with leather case I was thinking about selling and wondering if you would be interested in buying it
#6 julian m bucknall said...
05-Sep-11 9:40 AMDavid: Thanks for making the offer, but one is all I "need". (I think need is the right word there ;).)
Cheers, Julian
#7 Daniel Kollay said...
08-Jan-15 8:49 AMGood Morning,
I have a DECI-LON K&E 68-1100 Slide Rule that needs a case. The one I had was green and purchased in 1965 but it needs to be replaced. Any ideas where I might find a replacement?
With Warm Regards Dan
#8 julian m bucknall said...
08-Jan-15 9:26 AMDaniel: My suggestion would be to monitor eBay for K&E slide rules. There may be a rule on sale that's seen better days, but that has a really good case. There are a few slide rule sites online that sell rules (an example), but there you'd be paying through the nose for an excellent rule just for the case.
No really good ideas, sorry.
Cheers, Julian
#9 Scott Fischer said...
31-Dec-15 7:26 AMI own one of these K&E slide rules. Have not used it since 1972. Took it out today to see if I could learn to use it again. Funny to be searching for the old stuff on the inet and getting hits. Seems to be quite the slide rule. I enjoyed reading about the company history. Regards, Scott PS. I upgraded to an HP29C.
#10 Bill McGrath said...
24-Jun-17 4:16 PMI have a Deci-Lon 68 1100 in like-new condition, along with the leather case - a few scuffs only - and the original owner's manual. S/N is 901703. I bought it when starting engineering school in 1967. Any idea what it would be worth today - June 2017?
#11 Bill Smith said...
18-Oct-17 5:02 PMI was recently given a Deci-Lon 10 that looks identical to yours, except: the serial number on mine is 246702, the red and black vertical lines on your slider are missing on mine, and the model number (located under the Deci-Lon 10 logo on yours) is missing on mine.
The copyright dates on mine are identical to yours, so there's that.
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